With the use of a scattered light distribution formed by reflected light rays from a surface of an object, the texture of the object can be quantified. The quantification of texture allows the analysis regarding the glossiness of a printed surface or the like or the analysis of appearance of the object. With the application of scattered light distribution data to computer graphics, the appearance or texture of the object can be appropriately represented. Accordingly, scattered light distribution data may be widely applicable, and the scattered light distribution may be required in various situations. The classification of the scattered light distribution may be based on two types of scattered light.
The first type is scattered light originating from a surface having a structure whose size is substantially equal to or less than the wavelength of illumination light to be incident on a target object. If the wavelength of visible light ranges from 400 nm to 760 nm, the size of this structure may be about 760 nm or may be less than 760 nm although it depends on the wavelength of illumination light to be incident. The scattered light of this type depends on the surface roughness of a structure with a size on the order of the wavelength of the illumination light and the wavelength, and is typically derived from electromagnetic field analysis. In this specification, the scattered light of this type is hereinafter referred to as “scattered light or scatter caused by the wave-optics components”.
The second type is scattered light originating from a surface having a structure whose size is greater than the wavelength of illumination light to be incident. The size of this structure may be about several micrometers to about several tens of micrometers or may be greater. The scattered light of this type is generated by diffuse reflection which depends on the angle of incidence of incident light and the inclination angle of the structure, and is derived from the general rule of reflection. The scattered light therefore does not depend on the wavelength of the illumination light but only depends on the structure of the surface of the object whose size is on the order greater than the wavelength of the illumination light. In this specification, the scattered light of this type is hereinafter referred to as “scattered light or scatter caused by the geometrical-optics components”.
A technique for obtaining a scattered light distribution is disclosed in Patent Citation 1. In this technique, a parameter indicating a surface structure and an effective refractive index are used to estimate the relative-specular glossiness of the surface.